1. Field of the Invention
The present invention relates generally to infusion devices. More particularly, the invention concerns an elastomeric bladder type infusion apparatus which is used for controllably delivering a beneficial agent to a patient. The device uniquely includes adjustable flow rate means for adjusting the rate of fluid flow from the device toward the patient.
2. Discussion of the Prior Art
Many types of infusion pumps embodying an elastomeric balloon or bladder for delivery of a quantity of pharmaceutically active material to a patient have been suggested in the past. For example, U.S. Pat. No. 4,915,693 issued to Hessel discloses an infusion pump comprising an elastomeric bladder having at least an open end, and an elongate stress member extending concentrically within the entire length of the hollow portion of the bladder and having a fluid tight seal therewith. Both a filling port and an exit port are provided in the stress member, each in fluid communication with the interior of the bladder by way of an influent and an effluent lumen, respectively. The stress member has a diameter that is greater than the relaxed internal diameter of the bladder, and has a length that exceeds the relaxed internal length of the hollow portion of the bladder, so that it prestresses the bladder in both the axial and radial directions when disposed therein, substantially filling the bladder in its unfilled state. The Hessel device also includes a one-way valve on the stress member which permits flow through the influent lumen only in the direction of the interior of the bladder.
Very early balloon type infusion devices are described in U.S. Pat. Nos. 3,468,308 and 3,469,578 issued to Bierman. These patents disclose a device for expelling a liquid from a bladder member at an extremely slow rate over an extended period of time.
One of the more advanced elastomeric bladder type devices ever developed is described in U.S. Pat. No. 5,354,278 issued to the present inventor. Because the present invention comprises an improvement to the devices disclosed in this latter patent, U.S. Pat. No. 5,354,278 is hereby incorporated by reference as though fully set forth herein. Another advanced elastomeric bladder type device is disclosed in U.S. Ser. No. 08/729,326 filed by the present inventor on Oct. 15, 1997. This application is also incorporated by reference as though fully set forth herein.
Disclosed in U.S. Pat. No. 5,721,382, issued to one of the present inventors, is a device having a flow indicator means similar to that embodied in the present invention. For this reason, U.S. Pat. No. 5,721,382 is incorporated by reference as though fully set forth herein.
None of the prior art devices known to applicant have the unique capability of the present invention for precisely adjusting the rate of fluid flow from the device toward the patient using an elegantly simple, built-in, flow-rate adjustment mechanism.